It is known to surface image or analyze multiple sample spots by scanning a laser beam over a sample plate such that ions are introduced at the optical axis of a mass spectrometer. For example, MALDI or DE-MALDI analysis has been conducted using a multi-spot sample plate.
It is also known to image a sample with a Time of Flight (TOF) mass spectrometer comprising electric sectors, such as in U.S. Pat. No. 5,128,543. Such analyzers typically image a small sample area by illuminating the sample with a homogeneous ion beam or laser, and then using toroidal or spherical electric sectors to transfer the resulting sample ions to a position sensitive detector in a manner that provides point to point imaging. These analyzers provide first order time-per-energy focusing and posses imaging properties, i.e. provide point to point transfer with first order tolerance to angular and energy spreads. Thus, two dimensional imaging and mass measurement may be performed simultaneously. Such analyzers may have a spatial resolution of approximately 1 micron for a 1 mm field of view, while providing a mass resolution of approximately 1000.
However, such electric sector based TOF instruments have low order time of flight and spatial focusing aberrations, and have multiple second order aberrations that are not compensated for. For example, due to third-order spatial and second-order TOF chromatic aberrations, sector-based imaging TOF mass spectrometers can only be applied to microscopy analysis of surfaces in case analyzed ions have a small energy spread, otherwise mass resolution is destroyed by large chromatic TOF aberrations. Also, multi-sector TOF mass spectrometers are not suitable for the analysis of a large field of view due to their large spatial third-order aberrations, mainly induced by fringing-field effects in the electrostatic sector fields. As such, these systems do not provide high mass resolution and are poorly suited to imaging relatively large fields of view, e.g. above 1 mm.
It is therefore desired to provide an improved time of flight mass spectrometer and an improved method of time of flight mass spectrometry.